What's the general view on plunging?
 

Is there an agreed attitude to watering by plunging rather than with a hose or watering can? I find that my plants take up much more water from plunging than from overhead watering and I can be certain that all of the roots are getting water. It also uses much less water.

Is there a downside to plunging?

Lots of people water this way. It depends on how many plants and how much time you have.

The only downside to soaking (or plunging as you call it) is the risk of spreading disease if you soak the plants in the same water. You need individual containers to soak each plant, or change the water/rinse container between each plant, so I'm not sure it saves much water depending on the size of your collection.

Yes, that's true. Of course, we all like to think that none of our plants are diseased but the possibility is always there.

I'll restrict plunging to my Psychopsis which are the ones that appear to benefit most.

Soaking plants together or not depends on the level of risk that you are comfortable with.
I used to soak plants together because it saved time, then had a diseased plant so stopped doing that. I now only soak the ones that most benefit from it, and for the others that are watered a different way, I'll just soak them once in a while.

One significant advantage to overhead watering (meaning using a hose with water breaker, giving you hand-held "rain") is that it both oxygenates the water and aerates the potting medium, flushing the stagnant air out of it.

If your plants aren't getting sufficient water when irrigated in that manner, either simply repeat the process after a 15-30 minute wait, or water more frequently, which is better for the plant anyway.

Thanks
 

Thanks to all for useful advice

I do what Ray suggested and I water once then water again a few minutes later if the roots didn't absorb enough water the first time. For the orchids that really want more water, I use a shallow saucer or bowl underneath which keeps a little water in the bottom. I use basket pots and lava rock so this helps keep the roots happy. I also have learned that if the roots don't green fairly quickly when watering, it usually means that I should water more often.

Ray has emphasized and various evidence shows that the fertigation process is as important for removing the bad stuff (waste from the root zone and maybe bad air) as for inputting good stuff. Watering from above lets gravity remove the bad stuff out the bottom. If you consecutively dunk plants in a common container, you are progressively contaminating the solution with wastes from each pot.

Bad stuff might also mean excess nitrogen from the rotting (decaying) wood in potting media. Excess nitrogen (I believe until told otherwise) could "brown" the roots of plants because it acts similar to too much nitrogen in fertilizer. That is why I observe (not scientific) that inorganic medium is much better for the root systems of epiphytic orchids.